In a known way, there are known joysticks for the control of a machine comprising a function block provided with a mechanical member which can be moved directly by the hand of a user to initiate dispatch of a command controlling the machine or a display of information on the present status of the controlled machine, an outer shell formed by joining two rigid half-shells, these half-shells tightly enclosing the function block each on their respective sides, each half-shell comprising for this purpose a joint surface all along its perimeter which follows a three-dimensional path terminating on itself and extending in the three dimensions of space, this joint surface, bearing against the corresponding joint surface of the other half-shell in a first joint zone, and bearing against the periphery of the function block in a second joint zone, this second joint zone being contiguous with the first joint zone, a sealing element comprising a sealing cord extending continuously along the three-dimensional path between the joint surfaces in the first joint zone, to ensure that this first joint zone is watertight, and a ring seal taking a complete turn around the function block and located at the second joint zone to ensure that this second joint zone is watertight, this annular seal having a transverse cross-section which differs from the transverse cross-section of the sealing cord.
In known joysticks the joint surfaces have a complex three-dimensional shape, particularly because of ergonomic considerations. Furthermore, typically, the sealing cord and the ring seal have different transverse cross-sections. Thus in these known joysticks the sealing cord and the ring seal are two separate parts which are mechanically independent of each other because the first and second joint zones have very different shapes. Through the use of such seals, instead of an adhesive or a similar product, the joystick can be easily dismantled during maintenance operations on the joystick, and then reassembled using the same parts. Manufacture of the seals is also simple and inexpensive. In addition to this, maintenance can be carried out manually and without the need for complicated and costly equipment. Finally the dimensions and weight of the joystick are reduced to a minimum. However it has been found that these joysticks are not wholly satisfactorily watertight. For example it has been found during tests that water droplets have succeeded in penetrating within the joystick, which could for example damage functioning of the function block.
There is therefore a need for a control joystick for a machine which has the same advantages as known joysticks while being more watertight.